Electronic circuits are designed with the aid of an information processing apparatus. Generally a circuit is made up of a variety of elements, which include integrated circuits (IC), resistors, capacitors, and other electronic components. Also included are terminals for power supply and ground connections. These components are interconnected by wiring lines so that the circuit as a whole will provide particular intended functions.
Computer-aided design (CAD) is one of the tools that assist in the creation of a circuit design. CAD software running on a computer offers a graphical user interface (GUI) dedicated for circuit design. For example, the design engineer places component symbols and draws wiring lines to connect them in a GUI window on the display device.
The connections of components in a circuit may be managed by using net identifiers (net ID) assigned to each pin of components. When two or more pins have the same net ID, it means that they are wired together. The designer sometimes needs to check differences between two circuits. One proposed method achieves this by identifying each pair of corresponding pins in master and slave circuits and, with those pins, matching net IDs in the slave circuit with those in the master circuit one by one. If some net IDs remain with no counterparts, then each of these net IDs indicates a difference between the two circuits. See, for example, the following documents:
Japanese Laid-open Patent Publication No. 7-239870
Japanese Laid-open Patent Publication No. 2008-009574
The above-noted method compares two circuits in their entirety, meaning that the matching process searches even unnecessary part of the circuits. This extraneous processing could be a drawback in some cases, such as when an existing circuit is imported to the circuit under development. The design engineer may need to check the imported portion as to what is different between the existing circuit and the circuit under development. However, the processing of a whole-to-whole comparison extends over the circuit section that is unrelated to the imported circuit, thus leading to increased processing costs. Such extraneous comparison would also result in detection of extraneous differences, making it difficult to figure out which differences are really relevant.